Rainbow-colored clouds, known as iridescent clouds, were spotted over parts of Victoria during the weekend. Observers in the Melbourne suburbs of Mount Waverley and Caroline Springs captured photographs of the rare event. These clouds, which display a shimmering spectrum of colors, are a fascinating optical phenomenon that occurs under specific atmospheric conditions. According to Sarah Scully, a senior meteorologist at the Bureau of Meteorology, such occurrences are not unheard of in Australia but are seldom noticed or photographed. "People don't often notice them, as they're really fleeting," she explained. Iridescent clouds typically form from cirrus clouds, which were present in Victoria during the weekend. These high-altitude clouds are composed of ice crystals and are found in the colder regions of the troposphere, the lowest layer of Earth's atmosphere. The rainbow effect in these clouds happens when sunlight is diffracted—bent—around the ice crystals. This phenomenon is most visible in newly formed clouds where the ice crystals are uniform in size. Smaller clouds allow more sunlight rays to pass through and be diffracted by individual ice droplets, enhancing the colorful effect. The colors spread in rings or waves due to the diffraction process, creating a mesmerizing visual display. Iridescent clouds are often confused with sun dogs, another optical phenomenon that shares some similarities. Scully explained that sun dogs appear as bright spots on either side of the sun, caused by light refracting through water ice crystals in the atmosphere. These usually occur at lower altitudes and near the horizon. "You need it to sit even lower [than an iridescent cloud]," she noted, highlighting the key differences between the two phenomena. While both involve light interacting with atmospheric particles, the specific conditions and positions of these particles create distinct visual effects.